tsort: allow independent nodes

[mknos]

• When a node refers to itself in a pair it means the node exists but does not depend on anything
• Previously, this input would result in a "cycle" error
• In my test file, allow node 'd' to be added to hash %npred with predecessor count of zero, so it then appears in list @list
• The inner "foreach" loop does not execute for node 'd' because it has no dependency; it has no need for an entry in hash %succ

%perl cat in.tsort2
a b
b
  c
d d
%perl tsort.old in.tsort2
a
b
c
tsort.old: cycle detected
%perl tsort in.tsort2 # patched
a
b
c
d
%perl cat in.tsort3
a a
%perl tsort in.tsort3 # output agrees with GNU tsort
a

[coveralls]

Pull Request Test Coverage Report for Build 11356756634

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 73.805%

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Totals
Change from base Build 11349099383:	0.0%
Covered Lines:	355
Relevant Lines:	481

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💛 - Coveralls

[briandfoy]

changes: allow nodes to refer to themselves (has no dependency). This previously created a cycle error.